This invention relates to a fuel injector for injecting fuel, fed under pressure from a fuel injection pump, into a combustion chamber of an engine.
A fuel injector disclosed in Japanese Laid-Open Patent Application No. 1-92569 comprises an elongate hollow nozzle body having a closed lower end, and a needle valve mounted within the nozzle body. This nozzle body includes a fuel reservoir chamber, a tapered valve seat formed on the inner surface of the lower end portion of the nozzle body, and a pair of injection ports (that is, first and second injection ports) formed in the lower end portion of the nozzle body. The angle of the first injection port with respect to the axis of the nozzle body is acute whereas the angle of the second injection port with respect to the axis of the nozzle body is generally 90.degree.. The inner ends of the first and second injection ports are disposed at the valve seat of the nozzle body, and are disposed at the same position in the direction of the axis of the nozzle body. The outer ends of the first and second injection ports are spaced apart from each other. On the other hand, the needle valve has a pressure receiving portion exposed to the fuel reservoir chamber, and a tapered conical abutment portion formed at its lower end portion. The needle valve is urged by a spring, so that its abutment portion is seated on the valve seat. In this seated condition, the inner ends of the first and second injection ports are closed by the outer peripheral surface of the abutment portion. The pressure of fuel fed into the fuel reservoir chamber from a fuel injection pump acts on the pressure receiving portion to cause the needle valve to lift against the bias of the spring, so that the abutment portion is brought out of contact with the valve seat. As a result, the first and second injection ports are opened to inject the fuel into a combustion chamber of an engine.
The fuel injector of the above patent publication is mounted on the engine in inclined relation to the axis of an engine cylinder, and therefore it is expected that the first and second injection ports are inclined at generally the same angle relative to the axis of the engine cylinder. In this case, the fuel is injected simultaneously from the first and second injection ports at the same inclination angle relative to the axis of the engine cylinder. Therefore, the fuel can not be injected into the combustion chamber over a wide range.
Let's assume that the above fuel injector is mounted in parallel relation to the axis of the engine cylinder. When the needle valve is lifted, the fuel is injected simultaneously from the first and second injection ports at difference angles relative to the axis of the engine cylinder. In this case, the distribution of the fuel in the combustion chamber is extremely uneven.
In the fuel injector of the above patent publication, since the outer ends of the first and second injection ports are spaced apart from each other, the effect of making the fuel particles fine as achieved in the present invention can not be expected.
Japanese Laid-Open Utility Model Application No. 62-87171 discloses a fuel injector comprising a nozzle body and a needle valve. The nozzle body has a tapered valve seat formed at a lower end portion thereof, and a small chamber provided below this valve seat. A single first injection port and a plurality of second injection ports are formed in the lower end portion of the nozzle body, and the angle of inclination of the first injection port is different from that of the second injection ports. When the fuel injector is slightly obliquely mounted on an engine, the first injection port extends generally horizontally, and the second injection ports extend obliquely downward. The inner end of the first injection port is open to the valve seat, and the inner ends of the second injection ports are open to the inner peripheral surface of the small chamber. The needle valve has at its lower end portion a tapered conical abutment portion and a throttle portion formed at the lower end of this abutment portion. When the abutment portion is seated on the valve seat, the throttle portion is extended into the above small chamber. In this seated condition, the inner end of the first injection port is closed by the outer peripheral surface of the abutment portion, and the inner ends of the second injection ports are closed by the outer peripheral surface of the throttle portion. When the needle valve lifts, the abutment portion is brought out of contact with the valve seat at an initial stage at which the amount of lift is small, so that the first injection port is opened, thereby injecting the fuel from the first injection port toward an ignition plug. At this initial stage, the throttle portion remains received in the small chamber, and therefore the second injection ports are kept closed. When the needle valve further lifts, the throttle portion comes out of the small chamber, so that the second injection ports are opened, thereby injecting the fuel from the second injection ports.
In the fuel injector of the above Japanese Laid-Open Utility Model Application No. 62-87171, the fuel is injected from the first injection port only toward the ignition plug when the amount of lift of the needle valve is small, and therefore the fuel can not be supplied into the combustion chamber over a wide range. Further, since the outer ends of all the injection ports are spaced apart from one another, the fuel particles can not be made fine.
Japanese Laid-Open Utility Model Application No. 57-158972 discloses a fuel injector similar to the fuel injector of the above Japanese Laid-Open Utility Model Application No. 62-87171. This fuel injector has first and second injection ports which are inclined at the same angle. When the lift of a needle valve is small, fuel is injected from the first injection port, and when the lift is large, the fuel is injected from the first and second injection ports. In this fuel injector, the direction of the fuel injection is not changed regardless of the amount of lift of the needle valve, and therefore, the fuel can not be supplied into the combustion chamber over a wide range. Further, since the outer ends of all the injection ports are spaced apart from one another, the fuel can not be made fine.
Technology Reports of Tohoku University (Vol. 22, No. 2, pages 157 to 164, issued Mar. 25, 1958; Editor: Engineering Department of Tohoku University; Publisher: Tohoku University) discloses a fuel injector comprising a nozzle body and a needle valve. The nozzle body has an equalizer chamber at its lower end portion, and a valve seat provided above this equalizer chamber. A plurality of pairs of first and second injection ports are formed in the lower portion of the nozzle body, and are spaced circumferentially of the nozzle body. The first injection ports extend obliquely downward relative to the axis of the nozzle body, and the second injection ports extend perpendicularly to the axis of the nozzle body. The inner ends of the first injection ports are disposed above the inner ends of the second injection ports. The inner ends of the first and second injection ports are open to the equalizer chamber. Each pair of first and second injection ports have a common outer end. In this fuel injector, since the inner ends of the first and second injection ports are open to the equalizer chamber, the fuel is injected from the first and second injection ports when the needle valve lifts, so that the fuel can be injected at a wide angle. However, the pressures at the inner ends of the first and second injection ports are equal to each other, and the fuel is injected simultaneously from the first and second injection ports, and therefore the direction of injection of the fuel can be not selected in accordance with the amount of lift of the needle valve. Further, since no pressure difference occurs at the common outer end of the first and second injection ports, a cavitation is not produced, and it can not be expected to make the fuel particles fine.
Japanese Laid-Open Utility Model Application Nos. 56-129568 and 1-158553 respectively disclose lift control mechanisms similar in basic construction to lift control mechanisms used in two embodiments of the present invention.
The inventor of the present invention earlier filed a U.S. patent application Ser. No. 07/803,587 on Dec. 9, 1991 directed to a fuel injector similar to the fuel injector of the present invention, and its German counterpart is P4142430.1 filed on Dec. 20, 1991.